Deceleration-responsive press guard device

ABSTRACT

A safety device for a power press prevents an operator from reaching into the area of the press die when the press fails to stop as scheduled. The device includes a deceleration sensing arrangement which controls the operation of an actuator for a press guard, the press guard remaining in a &#39;&#39;&#39;&#39;prevent&#39;&#39;&#39;&#39; position unless the operating cycle of the press includes the proper deceleration period.

United States Patent Van Houten [45] Mar. 14, 1972 [54]DECELERATION-RESPONSIVE PRESS GUARD DEVICE [72] Inventor: George L. VanHouten, 186 Rensselaer Road, Essex Fells, NJ. 07021 [22] Filed: Nov. 12,1969 [21] Appl. No.: 875,632

[52] ILLS. Cl ..100/53, 74/615, 83/397, 192/133 [51] int. Cl ..B30b15/00 [58] Field olSearch ..100/53; 74/612-615; 83/397; 192/130, 133,134

[56] References Cited UNlTED STATES PATENTS 2,683,515 7/1954 l-lorn etal ..192/134 2,888,123 5/1959 Madden ..l92/l34 FOREIGN PATENTS ORAPPLICATIONS 603,934 6/1948 Great Britain 100/53 Primary Examiner-Billy.l. Wilhite Attorney-Larson, Taylor and Hinds [57] ABSTRACT A safetydevice for a power press prevents an operator from reaching into thearea of the press die when the press fails to stop as scheduled. Thedevice includes a deceleration sensing arrangement which controls theoperation of an actuator for a press guard, the press guard remaining ina prevent" position unless the operating cycle of the press includes theproper deceleration period.

2 Sheets-Sheet 1 mmvm'nwum GEORGE L. VAN HOUTEN ATTUIRN EWS Pmmmd arch1% 1% 2 Sheets-Sheet 2 5 m 7 a Q 20 AND Z4 70 AIR SUPPLY INVENTOR.GEO/P65 L VAN HOUTE/V lDlECELEItATION-RESPONSIVE PRESS GUARD DEVICEFIELD OF THE INVENTION The present invention relates to power pressesand the like and more particularly to an arrangement for protecting anoperator of such a press against injury when the press fails to stop asscheduled.

BACKGROUND OF THE INVENTION A large number of the more serious accidentsinvolving presses occur when a press, which is operating on asinglecycle" basis, malfunctions and fails to stop at a predeterminedtime in the cycle. Under these circumstances the press operator, who inmany instances will have become accustomed to the rhythm of thesingle-cycle operation of the press, may attempt to reach into the pressdie, in accordance with his normal actions, to remove a finished part orto insert new blank and may, in so doing, be injured.

Single-cycle operation of a press is utilized when the parts to beformed by the press must be fed by hand into the press die, removed byhand from the die or both. To initiate such operation, the press brakeis disengaged and the clutch is engaged so that the press crankshaftaccelerates up to the working speed of the press and is carried throughthe working or closing portion of the cycle wherein the press die isclosed. As the die reopens, the clutch is disengaged and brake isapplied at a time such that the press crankshaft is caused to decelerateand stop at the top of the stroke. Thus for normal single-cycleoperation, the stroke cycle includes a period of deceleration in laststage thereof, the precise length of this period as well as of theacceleration period being a function of the speed at which the press isto be operated as well as of the characteristics of the brake andclutch. A repeating stroke is one where there is no deceleration orinsufficient deceleration to provide stop page of the press, the presscontinuing to operate at full working speed during what is normally thedeceleration period in the cycle so that the press continues past topdead center and acts to reclose the die.

Press guards of the prior art are designed to remove the press operatorfrom danger if and when the press is reclosing. As the operating speedsof such presses increases, the amount of time available to remove theoperator from danger grows correspondingly small. Although the guardsand the stops thereof must be made stronger and heavier for operation atthese higher speeds, this approach is in many instances self-defeatingin that as the momentum increases, the resultant wear and breakageduring normal operation is correspondingly increased. Further, as thesedevices are made stronger to operate at increased speeds the danger fromthe devices themselves increases.

SUMMARY OF THE INVENTION In accordance with the present invention apress is provided which includes means for sensing or detecting theeffectiveness of the braking action on the press ram or, stateddifferently, the presence of the proper deceleration period in theoperating cycle, and means for controlling the operation of a pressguard, responsive to the sensing means. The press guard is movablebetween a first, prevent position wherein access to the press die isprecluded and a second, permissive position wherein access to the pressdie is permitted. An actuator for the press guard which is responsive tothe sensing means provides movement of the press guard to the permissiveposition thereof when the operating cycle includes the properdeceleration period.

The actual physical embodiment of the invention may take a number offorms. In an exemplary embodiment the press guard is formed by a plateor sheet of metal of the like which is positioned between the operatorand the press die in the prevent position thereof and is movable througha 90 arc to the permissive position thereof wherein the guardplate isflush with fixed die member of the press. A pneumatic actuator forguardplate is controlled by a control switch which is actuatedresponsive to a deceleration sensing arrangement including a first cammember secured to the press crankshaft and a second cam member whichfloats with respect to the camshaft. A stop member which extendsoutwardly of the fixed cam is received in a slot in the floating cam andrecesses in the peripheries of the cam surfaces, when aligned, permitinward movement of an actuator for the control switch. In operation thefloating cam falls behind the fixed cam during the acceleration periodof the operating cycle of the press to cause misalignment of the camrecesses and, consequently, prevents actuation of the control switchduring this period. The floating cam should catch up with the fixed camduring the deceleration period so that the cams are aligned and thecontrol switch is actuated. If the floating cam is not aligned with thefixed cam, the control switch is not actuated and the guard plateremains on the prevent position.

Other features and advantages of the invention will be set forth in orapparent from the detailed description of a presently preferredembodiment thereof found hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic representationof the basic operating elements of a power press;

FIG. 2 is a side elevational view of an exemplary embodiment of asimplified press incorporating the present invention;

FIG. 3 is a rear elevational view of the embodiment of FIG. 2 partiallybroken away to show the barrier guard;

FIG. 4 is a schematic circuit diagram of the electrical control systemfor the embodiment of FIGS. 2 and 3;

FIG. 5 is a perspective view of a schematic representation of oneembodiment of the deceleration sensing device of FIGS. 2 and 3; and

FIGS. 6 and 7 are end views, drawn to a reduced scale, of the sensingdevice of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, aschematic representation of a typical press, generally denoted P isshown. The press P is of conventional construction and this constructionwill be only briefly considered for purposes of completeness ofdisclosure and to provide a general background as an aid inunderstanding the present invention. The press P includes a die denotedD including a movable die member 10 and a fixed die member 12, areciprocating motion being imparted to movable die 10 through a ram orslide 14 driven by a crankshaft 16. A drive l8 for crankshaft 16 maytypically comprise a motor which drives a flywheel. The motor takes acertain period of time to bring the flywheel up to full speed and henceenergy is stored therein, this energy being available for use during theheavy working portion of the stroke of ram 114. A clutch indicated at 20connects drive 18 to crankshaft 16 which is connected to ram 14 througha bearing arrangement indicated schematically at 22. The reciprocatingmotion imparted to ram 16 is used to open and close the die D. A brake24 is utilized to stop rotation of crankshaft I6 and to prevent rotationthereof as desired.

Referring to FIGS. 2 and 3, a simplified representation of a pressincorporating the present invention is shown. The press of FIGS. 2 and3, which is denoted 30, is of the general type shown schematically inFIG. 1 with certain elements thereof omitted for purposes of clarity ofillustration. Press includes a frame 32 which rotatably supports acrankshaft 34 driven by a flywheel 36 as described hereinabove. A ram orslide 38 is drivenly connected to crankshaft 34 and carries a movabledie member 40. Movable die member 40 cooperates with a fixed die member42 mounted on a base portion of frame 32 to form a die generally denoted44.

A flap or barrier guard 46 is positioned between an operator indicatedat 48 and the die 44, the operator of the press 30 facing the press asshown in FIG. 2.. Flap guard 46 is constructed of sheet metal, plasticor the like and is mounted on a metallic shaft 50 by suitable means (notshown) such as inino-l mu brackets. The shaft 50 is mounted in bearings(not shown) secured in the sides of press frame 32. Flap guard 46 in thevertical or prevent position thereof, shown in solid lines in FIG. 4,prevents access to die 44 whereas in the horizontal or permissive"position thereof, shown in dashed lines in FIG. 4, permits access to die44. In the permissive position thereof, guard 46 forms a horizontaltable which is even with the lower, fixed die member. Movement of flapguard 44 is controlled by a rotary actuator 52 which provides 90 angulardisplacement of guard 46 between the vertical and horizontal positionsthereof.

It will be appreciated that a number of devices may be utilized inproviding rotation of shaft 50 and hence of guard 46. For example,actuator 52 may be pneumatically operated and may as shown in FIG. 4,include a series of vanes 52a located within a cylindrical housing 52b,which vanes, responsive to air pressure from a solenoid-controlled valve53, provide rotation of shaft 50 through a 90 arc and consequentrotation of guard 46 between the prevent and permissive positionsthereof. As is described in more detail hereinbelow actuation ofactuator 52 is controlled by a control device 54 in accordance with theacceleration and deceleration cycle of the press 30.

Referring again to FIG. 4, the electrical control circuit for press 30is shown. The circuit includes input terminals 56 and 58 which areconnected to a source of electrical energy (not shown). A double-pole,single-throw foot switch 60, actuated by the operator of the press,completes a circuit through a first set of contacts 60b in a first line64 in a first (or at rest) position thereof and completes a circuitthrough a second set of contacts 60a in a second line 62 for a second(or actuated) position thereof, line 62 being open for the firstposition of switch 60 and line 64 being open for the second position ofswitch 60.

A flap switch 66 and a press clutch solenoid 68 are connected in seriesin line 62. Flap switch 66 comprises a normally open microswitch mountedas indicated in FIG. 4 such that actuation thereof is effected inresponse to movement of flap guard 46 to the permissive positionthereof. Switch 66 is shown in the actuated position thereof in dottedlines in FIG. 4 and is, as stated, actuated by movement of flap guard 46to the prevent position thereof, this position of flap guard 46 alsobeing indicated in dotted lines in FIG. 4. As shown in FIG. 4, pressclutch solenoid 68 controls actuation of an air valve 77 and aircylinder 79 for controlling operation of a press clutch corresponding toclutch of FIG. 1. Energization of solenoid 68 causes engagement of thepress clutch and operation of the press 30 and deenergization thereofcauses disengagement of the press clutch and stopping of press 30.

Line 64 includes a ram switch 70, a set of relay contacts 72a and a flapvalve solenoid 74. Relay contacts 72a are normally open and actuationthereof is controlled by a relay 72 connected in parallel with flapvalve solenoid 74 and foot switch contacts 60b. Relay contacts 720 areconnected in parallel with a deceleration signal-responsive switch 76.Ram switch 70 comprises microswitch responsive to movement of press ram38, switch 70 being normally open and being closed with ram 38(indicated schematically in FIG. 4) in the extreme upward positionthereof. Flap valve solenoid 74 is used in controlling four-way airvalve 53 which in turn controls actuation of flap guard actuator 52described hereinabove. With solenoid 74 deenergized, flap guard 46 is inthe prevent position thereof. Thus it is necessary to energize solenoid74 before flap guard 46 is moved to the permissive" position whereinaccess is provided to the press die 44.

With the press at rest, the crankshaft 34 at top dead center, and switch60 in the first, or at rest position, relay 72 and solenoid 74 areenergized through contacts of ram switch 70, relay contacts 720, andswitch contacts 60b. As the switch 60 is moved to the second (oractuating) position, contacts 6011 are opened'and contacts 60a areclosed. Solenoid 74 is deenergized, causing the four-way valve (notshown) to shift and cause rotation of flap guard 46 to the preventposition.

When the flap guard 46 is in the full prevent position, flap switch 66is closed. An electrical signal is now transmitted through the switchcontacts 60a and flap switch 66 to press clutch solenoid 68, causingpress clutch 20 to be engaged and press brake 24 to be released. At thistime press crankshaft 34 starts rotating, causing slide 38 to descendand close press die 44. The first downward motion of slide 38 causes ramswitch 70 to open and deenergize relay 72. The operator then releasesswitch 60, which returns to the first, or at-rest, position thereof,with contacts 60b closed and contacts 60a open. As the press cycle iscompleted and ram 38 again returns to the upper position thereof ramswitch 70 is closed. If the proper braking action, and thereforedeceleration occurs at this time, the deceleration-responsive switch 76will close and energize relay 72, and at the same time, through switchcontacts 60b, energize solenoid 74. Solenoid 74, now energized, causesthe four-way valve (not shown) to shift position and cause flap guard 46to move to the permissive" position, and permit the operator to haveaccess to the die area. If the driving force through clutch 20 is notreleased, or the braking action of press brake 24 is not effective,deceleration does not occur in the proper amount and thedeceleration-responsive signal switch 76 will not close. Under theseconditions, relay 72 and flap valve solenoid 74 remain deenergized andthe guard remains in the prevent" position.

Referring to FIGS. 5 to 7, one form of deceleration-respom sive controldevice 54 indicated in FIGS. 2 and 3 is shown. Control device 54 ismounted on, or driven by, crankshaft 34 and includes first and seconddisclike cam members 80 and 82. Cam member 80 is rigidly affixed tocrankshaft 34 and rotates therewith whereas cam member 82 althoughmounted concentrically with crankshaft 34 floats with respect thereto.Floating cam 82 includes an outwardly extending stop member orprojection 82a which is received in an arcuate slot 800 in fixed cam 80.Slot 80a and stop projection 82a thus cooperate to limit movement offloating cam 82 with respect to fixed cam 80. Floating cam 82 includes arecess or notch 82b in the periphery thereof whereas fixed cam 80includes a similar notch or recess 80b. Deceleration-responsive sensingswitch 76, shown schematically in FIG. 4, includes an actuator 76aadapted to be received in recesses 80b and 82b upon alignment thereof asshown in FIGS. 5 and 6 and biased toward the periphery of cams 80 and 82as is indicated schematically by spring 76b in FIG. 4. Switch 76, whichis normally open, is closed in the position for actuator 760 shown inFIGS. 5 and 6, that is, upon alignment of recesses 80b and 82b.

Considering the operation of control device 54, upon rotation ofcrankshaft 34 floating cam 82 will fall behind fixed cam 80 and,assuming clockwise rotation of shaft 34, stop member 82a will bepositioned near or at the rearmost portion of slot 80a. As indicated inFIG. 7, under these conditions, switch actuator 76a will be heldoutwardly of the periphery of floating cam 82, recess 82b beingpositioned rearwardly of recess 80b. In this position switch 76 is openand flap guard 46 is in the prevent position thereof. If the press 30decelerates, the floating cam 82 will forge ahead of the previousposition thereof and will approach a position wherein stop member 82a ispositioned near or at the frontmost or leading portion of slot 80a.Under these circumstances recesses 80b and 82b are near alignment andswitch actuator 76a is permitted to move inwardly as shown in FIGS. 5and 6 so that switch 76 is closed.

All the overall operation of the press is believed to be apparent fromthe foregoing description, this operation will be very briefly reviewed.Under normal conditions, press 30 will operate as described, the normaloperating cycle including a period of acceleration, a working period anda period of deceleration. If, for example, a malfunction occurs in thecontrol system for controlling braking of crankshaft 34, the die 40 willreclose after the ram 38 again passes through top dead center. Reclosingof die 40 in this manner could cause possible injury to the pressoperator were it not for the presence of barrier guard 46. As discussedhereinabove when decelerationsensing device 54 senses that the properbraking of the rotational movement of crankshaft 34 is occurring, arelease signal is applied to actuator 52 which causes movement of guard46 to the permissive" position thereof so that the operator can gainaccess to die $0. lf, however, no such braking is detected by sensingdevice 54 a release signal is not applied to actuator 52 and guard 46remains in the prevent position thereof so that the operator isprotected.

Thus, although the invention has been described in detail with respectto exemplary embodiments thereof, it will be understood by those ofordinary skill in the art that, in addition to the modificationsspecifically described, other variations and modifications may beeffected within the scope and spirit of the invention.

lclaim:

l. A safety device for a press comprising a die including a stationarydie member and a movable die member, rarn means for causing movement ofthe movable die member, and a crankshaft for driving said rams means,said safety device comprising guard means movable between a first,prevent position wherein access to the die is precluded, and a second,permissive position wherein access to the die is permitted, guardactuator means for, upon actuation, causing movement of said guard meansbetween said first and second positions, and control means forcontrolling actuation of said actuator means, said control meanscomprising sensing means driven by the crankshaft for sensingdeceleration of said ram means, and switch means responsive to saidsensing means for controlling actuation of said guard actuator means,said sensing means including a first cam member fixed relative to thecrankshaft, a second, floating cam member movable relative to said firstcam member, shaft means for coaxially mounting said first and second cammembers in spaced relationship, and a stop member rigidly secured to oneof said first and second cam members, the other of said first and secondcam members including a slot therein for receiving said stop member,said first cam member including a peripheral cam surface including afirst arcuate recess therein and said second cam member including aperipheral cam surface including a second arcuate recess therein, andsaid switch means comprising a switch for controlling actuation of saidguard actuator means and a cam follower in engagement with theperipheral surfaces of said first and second cam members for controllingactuation of said switch, said cam follower being movable between afirst, nonactuating position and a second, actuating position, said camfollower, in the second, actuating position thereof, entering into saidfirst and second arcuate recesses when said recesses are in alignmentand movement of said cam follower into said recesses causing actuationof said switch and corresponding actuation of said guard actuator means,said cam follower being held in the first, nonaetuating position thereofwhen said arcuate recesses are out of alignment and hence preventingactuation of said guard actuator means and corresponding movement ofsaid guard means to the second, permissive position thereof,

1. A safety device for a press comprising a die including a stationarydie member and a movable die member, ram means for causing movement ofthe movable die member, and a crankshaft for driving said rams means,said safety device comprising guard means movable between a first,prevent position wherein access to the die is precluded, and a second,permissive position wherein access to the die is permitted, guardactuator means for, upon actuation, causing movement of said guard meansbetween said first and second positions, and control means forcontrolling actuation of said actuator means, said control meanscomprising sensing means driven by the crankshaft for sensingdeceleration of said ram means, and switch means responsive to saidsensing means for controlling actuation of said guard actuator means,said sensing means including a first cam member fixed relative to thecrankshaft, a second, floating cam member movable relative to said firstcam member, shaft means for coaxially mounting said first and second cammembers in spaced relationship, and a stop member rigidly secured to oneof said first and second cam members, the other of said first and secondcam members including a slot therein for recEiving said stop member,said first cam member including a peripheral cam surface including afirst arcuate recess therein and said second cam member including aperipheral cam surface including a second arcuate recess therein, andsaid switch means comprising a switch for controlling actuation of saidguard actuator means and a cam follower in engagement with theperipheral surfaces of said first and second cam members for controllingactuation of said switch, said cam follower being movable between afirst, nonactuating position and a second, actuating position, said camfollower, in the second, actuating position thereof, entering into saidfirst and second arcuate recesses when said recesses are in alignmentand movement of said cam follower into said recesses causing actuationof said switch and corresponding actuation of said guard actuator means,said cam follower being held in the first, nonactuating position thereofwhen said arcuate recesses are out of alignment and hence preventingactuation of said guard actuator means and corresponding movement ofsaid guard means to the second, permissive position thereof.